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April 17, 1962 H. D. CRANE 3,030,519

"AND" FUNCTION CIRCUIT Filed Jan. 20, 1958 A 54 Y I z) I y 50 so m x I i 34\ I 42 mom TRAISFf/F 6254/? fULJ PUAJZ Pl/ZJE INVENTOR.

HM/rr 0. c/mA i United States Patent 3,030,519 AND FUNCTION CIRCUIT Hewitt D. Crane, Palo Alto, Calif., assignor to Burroughs Corporation, Detroit, Mich, a corporation of Michigan Filed Jan. 20, 1958, Ser. No. 710,148 7 Claims. (Cl. 307-88) This invention relates to circuits for performing a logical and function, and more particularly, is concerned with an and function circuit employing magnetic core elements.

In copending application, Serial No. 698,633, filed November 25, 1957, now abandoned, in the name of Hewitt D. Crane and assigned to the assignee of the present invention, there is described a core register having a novel transfer circuit requiring no diodes or other impedance elements in the transfer loops between cores. The basic binary storage element of this circuit is an annular core having an input and output aperture therein. The binary zero digits are stored in the form of flux oriented in the same direction in the core on either side of the respective apertures, while the binary one digits are stored in the form of flux extending in opposite directions on either side of the respective apertures. Transfer is effected by applying a current pulse of predetermined magnitude to a coupling loop linking one aperture in each of two cores, one core constituting a transmitting core and the other core constituting a receiving core.

The present invention utilizes the principles of the above-identified copending application to accomplish the logical and function. According to the present invention, in order to transfer a binary one to a receiving core element, the identical flux condition representing a binary one digit must be established on each of a plurality of transmitting core elements.

In brief, the circuit of the present invention comprises a plurality of input or transmitting core elements and a single output or receiving core element. Each of the core elements is made of magnetic material having a high flux retentivity, such as ferrite, the core elements being annular in shape and having at least two small apertures therein. Each of the core elements is provided with a winding linking the annular core element through one of the apertures, the windings being connected in parallel across a pair of terminals. Means is provided for applying a transfer pulse across the terminals, the pulse being of a magnitude to produce a total current flow through the parallel windings which is slightly less than twice the threshold current required to reverse flux around any one of the annular elements when in a saturated condition. In this manner, unless all the input cores are set, i.e., unless the flux can be switched locally about the apertures of the transmitting cores, no flux change is effected in the receiving core in response to the transfer pulse.

For a more complete understanding of the invention, reference should be had to the accompanying drawings, wherein:

FIGS. 1 and 2 show a ferrite magnetic core element such as used in the present invention in two conditions of flux orientation; and

FIG. 3 shows a circuit according to the present inven tion for providing a logical and function and using the core elements of the type shown in FIGS. 1 and 2.

Consider an annular core, such as indicated'at in FIGS. 1 and 2, made of a magnetic material such as ferrite, having a square hysteresis loop, i.e., a material having a high flux retentivity or remanence. The annular core is preferably provided with two small apertures 12 and 14, each of which divides. the annular core into two parallel flux paths as indicated by the arrows. If a large current is pulsed through the central opening in the core 10, as by a clearing winding 16, the flux in the core may be saturated in a clockwise direction. The core is then said to be in a cleared or binary zero condition. If a large current is passed through either of the apertures 12 or 14, as by either of the windings 18 and 20, in the direction indicated in FIG. 2, and the current is of sufficient magnitude to cause switching of flux around the central opening of the annular core, a portion of the flux can be reversed so that the flux extends in opposite directions on either side of the respective apertures 12 and 14, as indicated by the arrows in FIG. 2. The core is then said to be in the set or binary one state.

The significant aspect of the transfer circuit described in the above-identified copending application is that with a given number of turns linking one of the small apertures in the core and with the core in its cleared state as shown in FIG. 1, a current exceeding a threshold value I must be provided to change the core to its set state as shown in FIG. 2. If the current does not exceed this threshold level, substantially no fiux is switched around the core. The aperture is said to be blocked when the current passing through the aperture must exceed the threshold value I in order to switch any flux in the core element.

On the other hand, if the core is already in its set state, a very small current, substantially less than the threshold value I causes flux to switch locally about the aperture. In this case the aperture is said to be unblocked. Thus if a current slightly less than the threshold current I, is passed through an aperture in a core element, flux will be switched or not switched within the core depend ing upon whether the core is in its cleared state or its set state, i.e., depending on whether the aperture is blocked or unblocked. I

This principle is used to provide a circuit producing an and function, as shown in FIG. 3. First, consider a transmitting core element 22 having an input aperture 24 and an output aperture 26. The transmitting core element 22 is coupled to a similar receiving core element 28 having an input aperture 30 and an output aperture 32. Each of the core elements 22 and 28 is provided with a clearing winding which passes current through the central opening of the core element, as indicated at 34 and 36 respectively. Suitable means is provided for generating clearing pulses through the respective windings 34 and 36, as by means of clear pulse sources indicated at 38 and '40 respectively. Thus each of the core elements 22 and 28 may be placed in the cleared state in which all of the flux is saturated in a clockwise direction in the manner described above in connection with FIG. 1. The output aperture 26 of the core element 22 is now blocked, as is the output aperture 32 of the core element 28.

A transfer loop 42 links the core element 22 through the output aperture 26 and the core element 28 through the aperture 30. A transfer pulse source 44, having a constant current characteristic, is coupled across the transfer loop 42. With both the core elements 22 and 28 in their cleared state, the current fiow produced by the transfer pulse source 44 divides between the portion of the loop 42 linking the output aperture 26 and the portion of the loop linking the aperture'30. The resistance in the two windings in the loop 42 is preferably arranged so that a substantially equal number of ampere-turns links the core 22 and the core 28. The current split is such that the current through each branch of the loop 42 is below the threshold required to switch flux in the respective cores and unblock the output apertures. As a result, with both the cores cleared, a trans fer pulse has no effect on either core.

' If, however, a large current has been pulsed through the input aperture 24 of the transmitting core element 22 at X so as to put the core .element 22 in its set state and unblock the output aperture 26, corresponding to the flux condition shown in FIG. 2, a different result takes place when a transfer pulse is generated by the source 44. In the latter case a much smaller current is required to reverse flux locally about the unblocked output aperture 26 in the transmitting core 22. As a result, with the core 22 in its set state, when a transfer pulse is applied across the loop 42, the current through the aperture 26 is sufficiently large to switch flux locally about the aperture 26. The impedance of the branch of the transfer loop 42 linking the aperture 26 is thereby momentarily increased due to the counter EMF generated by the switching flux. As a result, the current through the branch of the transfer loop 42 linking the receiving core element 28 through the aperture 39 increases above the threshold level required to switch flux about the central opening of the annular core element 28. As a result the core element 28 is left in its set state, following a transfer pulse from the source 44, when the transmitting core 22 is initially in its set state, thereby unblocking the output aperture 32.

According to the present invention, to provide a circuit having the logical and function, additional transmitting core elements 46 and 48 are provided. The clearing Winding 34 from the clearing pulse source 38 is arranged to link each of the transmitting cores 48, 46 and 22 in series for clearing all of the transmitting cores simultaneously and blocking all the output apertures. The transmitting coreelements 48 and 46 have separate input apertures 50 and '52 respectively, to which separate input current pulses at Y and Z may be applied. Output apertures 54 and 56 respectively of the core elements '46 and 48 are linked by windings which are connected in parallel with each other and in parallel with the transfer loop 42. Thus with four core elements as shown, the current from the transfer pulse source 44 divides between four parallel branches.

It will be seen that separate inputs X, Y, and Z are provided for each input core element by means of which each of the transmitting core elements 22, 46 and 48 respectively may be placed in the set state and the corresponding output apertures unblocked. With all of the core elements in the set state, the impedance of the branches of the transfer loop linking the transmitting core elements is high, so that a substantial portion of the current will pass through the input aperture 30 of the core element 28. In this manner the core element 28 is changed to its set condition.

However, if only two or less of the transmitting core elements 22,46 and 48 are placed in the set condition, insufficient current will pass through the branch of the transfer loop 42 linking the receiving core element 28 through the input aperture 30 to switch any flux therein. This is because at least one of the parallel branches of the transfer loop linking the input core elements presents a low shunting impedance, diverting current from the branch linking the output core element. Thus the receiving core element 28 will remain in its cleared state. For example, if the transmitting core elements 46 and 48 are in their set states and the transmittingcore element 22 is in its cleared state, current divides substantially equally between the portion of the transfer loop linking the transmitting core 22 through the aperture 26 and the receivingcore element 28 through the aperture 30, in which. case, as pointed out above, the ampere-turns linking the core element 28 is insufficient to switch any 'flux around the central opening of the annular core element.

It is desirable that bias be used on each of the transmitting and receiving cores in order to extend the operating current'range of the transfer pulseand to control the threshold level in'the receiving core according to the principlesv set forth in detail in the copending appli cation, Serial No. 704,511, filed December 23, 1957, in the name of Hewitt D. Crane and assigned to the assignee of the present invention. Thus as shown in FIG. 3, bias windings are provided on each of the core elements as indicated at 60, 62, 64 and 66. The bias windings are connected in series with each other and in series with the output of the transfer pulse source 44. turns that has been found to give satisfactory operation as follows:

Transfer loop windings linking the transmitting cores-- 12 turns.

Transfer loop linking the receiving care -11 turns.

Bias windings linking the transmitting cores2 turns.

Bias windings linking the receiving core--3 turns.

It should be understood, however, that operation of the and circuit does not depend on the use of bias as such. Moreover, the set of turns listed above is only one example of many sets of turns which are operative.

From the above description it will be seen that a circuit is provided which accomplishes the"and function. Only if all of the input or transmitting core elements are set can the output or receiving core element be set in response to a transfer pulse 44. In principle, any number of transmitting core elements may be connected in parallel. The advance pulse applied to the transfer loop, however, remains at the same current level. In practice, however, even the transmitting core elements that are in their set state draw some current through the corresponding parallel branches of the transfer loop, thereby diverting a corresponding current from the receiver core branch. This limits the practical number of parallel branches in the transfer loop. The circuit has been found to operate reliably with at least three input core elements.

'What is claimed is:

1. A logical and circuit comprising a plurality of input core elements and a single output core element of magnetic material having a high flux remanence, each of the coreelements being annular in shape with an input and an output aperture extending through each annular core element, means including windings linking each of the input core elements through the central openings therein provided by their annular shape for clearing all the flux in the input core elements to saturation in one direction, whereby the output aperture of each of the input core elements are blocked, a plurality of input windings, each input core element having an input winding linking the core element through an input aperture, where by the output apertures of any selected ones of the input core elements may be unblocked by a current pulse through the corresponding input windings, means including a'winding linking the output core element through the central opening therein provided by the annular shape of the core element for clearing all the flux in the output core element to saturation in one direction, a transfer circuit coupling each of the input core elements to the output core element, the transfer circuit including wind-' ings linking each of the input core elements through the output apertures-thereof and a winding linking the output core element through the input aperture thereof, the respective windings of the transfer circuit being connected in parallel with each other to provide a plurality of parallel current paths, and means for applying a trans-. fer pulse across the parallel windings of the transfer circuit, the pulse being of a magnitude to produce a total current flow through the transfer circuit equal toslightly less than twice the current required to produce flux reversal in a core element when in a saturated condition V the core elements being annular in shape to provide a a a large central aperture,.with an input and an output ape ture extending through each annular core element; means.

One set of for clearing all the flux in the input core elements to saturation in one direction, whereby the output aperture of each of the input core elements are blocked, a plurality of input windings, each input core element having an input winding linking the core element through an input aperture, whereby the output apertures of any selected ones of the input core elements may be unblocked by a current pulse through the corresponding input windings, means for clearing all the flux in the output core element to saturation in one direction, a transfer circuit coupling each of the input core elements to the output core element, the transfer circuit including windings linking each of the input core elements through the output apertures thereof and a winding linking the output core element through the input aperture thereof, the respective windings of the transfer circuit being connected in parallel with each other to provide a plurality of parallel current paths, and means for applying a transfer pulse across the parallel windings of the transfer circuit, the pulse being of a magnitude to produce a total current flow through the transfer circuit equal to slightly less than twice the current required to produce flux reversal in a core element when in a saturated condition as produced by said clearing means.

3. A logical and circuit comprising a plurality of input core elements and a single output core element of magnetic material having a high flux remanence, each of the core elements being annular in shape to provide a large central aperture, with an input and an output aperture extending through each annular core element, means for clearing all the flux in the input core elements to saturation in one direction, whereby the output aperture of each of the input core elements are blocked, a plurality of input windings, each input core element having an input winding linking the core element through an input aperture, whereby the output apertures of any selected ones of the input core elements may be unblocked by a current pulse through the corresponding input windings, means for clearing all the flux in the output core element to saturation in one direction, a transfer circuit coupling each of the input core elements to the output core element, the transfer circuit including windings linking each of the input core elements through the output apertures thereof and a winding linking the output core element through the input aperture thereof, the respective windings of the transfer circuit being connected in parallel with each other to provide a plurality of parallel current paths, and means for applying a transfer pulse across the parallel windings of the transfer circuit.

4. A logical and circuit comprising a plurality of input core elements and a single output core element, each of said core elements being made of magnetic material having a high flux retentivity, the core elements further being annular in shape to provide a large central aperture, and having at least two small apertures therein, each of the core elements having a winding linking the annular core element through one of said apertures, the windings being connected in parallel across a pair of terminals, means for applying a transfer pulse between said terminals, the pulse being of a magnitude to produce a total current flow through the parallel windings equalto slightly less than twice the threshold current level required to reverse flux around any one of the annular core elements when in a saturated condition.

5. A logical and circuit comprising a plurality of input core elements and a single output core element, each of said core elements being made of magnetic material having a high flux retentivity, the core elements further being annular in shape to provide a large central aperture, and having at least two small apertures therein, each of the core elements having a winding linking the annular core element through one of said apertures, the windings being connected in parallel across a pair of terminals, and means for applying a transfer pulse between said terminals.

6. An and circuit comprising at least three annular core elements of magnetic material having a square hysteresis characteristic, each of the core elements having a large central aperture and at least a pair of small apertures extending therethrough, one of the core elements being an output element and the remainder of the core elements being input elements, a plurality of input windings, one input winding linking one of the input core elements through one of said pair of small apertures, a plurality of transfer windings, one transfer winding linking one of the core elements through one of said small apertures, the transfer windings linking the input core elements being connected in parallel with each other and in parallel with the transfer winding linking the output core element, and means for applying a transfer pulse across the parallel paths formed by the transfer windings linking the input core elements and the single transfer winding linking the output core element, the current level of the transfer pulse being below the threshold required to switch a substantial amount of flux in any of the core elements when they are all saturated with all the flux in one direction.

7. An an circuit comprising at least three annular core elements of magnetic material having a square hysteresis characteristic, each of the core elements having a large central aperture and at least a pair of small apertures extending therethrough, one of the core elements being an output element and the remainder of the core elements being input elements, a plurality of transfer windings, one transfer winding linking one of the core elements through one of said small apertures, the transfer windings linking the input core elements being connected in parallel with each other and in parallel with the transfer winding linking the output core element, and means for applying a transfer pulse across the parallel paths formed by the transfer windings linking the input core elements and the single transfer winding linking the output core element, the current level of the transfer pulse being below the threshold required to switch a substantial amount of flux in any of the core elements when they are all saturated with all the flux in one direction.

References Cited in the file of this patent UNITED STATES PATENTS 2,741,758 Cray Apr. 10, 1956 2,742,632 Whitely Apr. 17, 1956 2,896,194 Crane July 21, 1959 OTHER REFERENCES Proceedings of IRE, vol. 44, issue 3, pp. 321-332, March 1956, by J. Rajchman and Lo, 

